In an internal combustion engine system having dedicated EGR (exhaust gas recirculation), one or more cylinders of the engine are segregated and dedicated to operate in a rich combustion mode. Because of the rich combustion, the exhaust gases from the dedicated cylinder(s) include increased levels of hydrogen and carbon monoxide. Rich combustion products such as these are often termed “syngas” or “reformate”.
Dedicated EGR engines use the reformate produced by the dedicated cylinder(s) in an exhaust gas recirculation (EGR) system. The hydrogen-rich reformate is ingested into the engine for subsequent combustion by the non-dedicated cylinders and optionally by the dedicated cylinder(s). The reformate is effective in increasing knock resistance and improving dilution tolerance and burn rate. This allows a higher compression ratio to be used with higher rates of EGR and reduced ignition energy, leading to higher efficiency and reduced fuel consumption.